Diabetes is a complex disease caused by hyperglycemia. As its essential treatment, the blood sugar level is controlled, in most cases by injection of insulin. What is really troublesome for those suffering from diabetes is, however, the advance to diabetic complications. As diabetic complications, diabetic retinopathy, diabetic nephropathy, diabetic angiopathy and diabetic neuropathy are known. In order to prevent the onset of diabetic complications or to retard the advance of them, proper blood sugar control is necessary over a long period of time. It is known that the longer the suffering period, the higher the incidence of diabetic complications.
As one of the factors for causing such diabetic complications, mentioned is abnormal acceleration of a polyol metabolic pathway (K. H. Gabbay, N. Eng. J. Med., 288, 831(1973)). The enzyme controlling this polyol metabolic pathway is aldose reductase (AR). An AR inhibitor is now used widely as a remedy for diabetic neuropathy. Diabetic complications occur not by one factor but by the tangle of various factors over a long period of time so that a medicament having mechanism of single action cannot be regarded as an absolute remedy.
An object of the present invention is therefore to provide a novel preventive and/or therapeutic agent for diabetic complications, particularly for diabetic neuropathy.